Many Silver Spring residents say they hope a Purple Line will someday provide a faster ride to Bethesda and other parts of the region. At the same time, they voice concerns about the impact of the transitway on their redeveloped restaurant and shopping district.

Some suggest that light-rail trains would travel too slowly and make traffic worse unless they run under the downtown area via a tunnel.

Some activists say the Purple Line's effects on the community's commercial area have gotten short shrift from Maryland transit planners, Montgomery County's elected officials and the news media when compared with the hubbub over trains potentially running along a popular wooded walking and biking path between Silver Spring and Bethesda.

They say their concerns stem from the fact that downtown Silver Spring, which has been rejuvenated over the past decade into a thriving entertainment district, has no land preserved for a transit line. Trains running aboveground, as state planners have proposed, would have to thread narrow streets crowded with vehicles and pedestrians. To the west, the state could use some of the trail land, which has been preserved since the 1980s. To the east through Prince George's County, trains would run along much wider roads and in more open areas.

"We've benefited tremendously from the rebirth of downtown Silver Spring, and we want to see it continue to be a vibrant and thriving community," said Mark Gabriele, president of the Seven Oaks-Evanswood Citizens' Association, which represents 700 homes east of downtown. Businesses would suffer, he said, if train-clogged streets "bring traffic to a standstill. . . . People will avoid areas with gridlock."

A 16-mile east-west Purple Line would connect Bethesda and New Carrollton inside the Capital Beltway. Light-rail trains, which are similar to trolleys and use overhead electrical wires, would run primarily aboveground and on local streets, mostly in their own lanes. They would cross some intersections at stoplights while running under or over others. Although the state has considered a rapid bus system, light rail has overwhelming support from the Montgomery and Prince George's councils, as well as both county executives.

The Maryland Transit Administration has studied ways to build a one-mile tunnel between the Silver Spring Metro station and Wayne Avenue at Cedar Street, near the parking lot at the Whole Foods store. But some Silver Spring residents say the state has not fully analyzed a 1.5-mile tunnel that would extend east beneath Wayne, emerging near Mansfield Road, east of Dale Drive.

The Montgomery council recently endorsed running light-rail trains through downtown Silver Spring with no tunnel. However, the council asked state planners to further study the longer tunnel option before Maryland Gov. Martin O'Malley (D) chooses a proposal to submit for federal funding.

The light-rail option endorsed by the council and Montgomery Executive Isiah Leggett would cost $1.2 billion. State planners say building a tunnel would add $150 million to $215 million, depending on the length. A higher price would hurt the Purple Line's chances when it competes against transit proposals from across the nation for relatively scarce federal construction money, said Michael D. Madden, the transit administration's manager of the study.

Madden said a tunnel could save passengers enough travel time to make it cost-effective. However, planners say they believe a tunnel would be too disruptive to residents on Wayne because the portal where trains would enter and exit the tunnel would require taking more land from ballfields. It also would require building retaining walls in front of three or four homes, whose occupants would have limited access to their driveways, he said.

Moreover, Madden said, running trains underground would limit a Purple Line's abilities to spur development, which is one of the project's primary goals, because that option probably would cut out one, and possibly two, downtown stations. Trains would bypass the restaurants, shops and other businesses that would otherwise draw people walking to and from a station, he said.

Gabriele said his citizens association wants the state to keep a tunnel as an option until more detailed engineering is done.

"Yes, it is more expensive," Gabriele said. "But in the long term when you're talking about a $1.5 billion infrastructure project that's expected to be there 50 to 100 years, don't you want it done correctly?"

Jonathan Jay, the civic association's vice president and a member of the Montgomery Planning Board's Purple Line advisory group, said residents on Wayne would lose even more land if the street had to be widened to accommodate aboveground trains.

"MTA is searching for reasons not to build a tunnel," he said.

Jay said he believes the trains' frequent stops would leave them "crawling" through downtown. He said trains crossing Georgia Avenue -- as frequently as every three minutes during the morning and evening rush periods -- would further clog the commuter route as stoplights are timed to favor the trains.

Madden said trains could travel as fast as 45 to 50 mph but would not exceed a street's speed limit. Although trains might get green lights extended by five or 10 seconds at some intersections, Madden said, current plans would give no priority to them at Georgia.

"It only takes seconds to get across" an intersection, Madden said. "It really doesn't cause a problem. You have traffic stopped at lights anyway."